To ensure security and authenticity in a worldwide supply chain, it is necessary to authenticate parts such as integrated circuit chips. Moreover, with the increasing use of electronic devices utilizing integrated circuits to provide different types of information for a variety of different applications, there has been an increasing need to adequately protect sensitive or critical information that may be stored within an electronic device to limit access to such information to only such other devices that have permission to access such information. Some examples of applications include the authentication of devices, protection of confidential information within a device, and securing a communication between two or more devices.
One type of chip identification (ID) utilizes electrical fuses (e-fuses). Typically, such identifiers are formed by providing on-chip fuses and/or anti-fuses, which are programmed (i.e., blown) at test. Blowing fuses and/or anti-fuses at test increases testing time and, thereby, increases chip manufacturing costs. Moreover, e-fuse based systems can be decoded (i.e., read) via failure analysis, and one part can be copied multiple times.
Another type of chip ID is a physically unclonable function (PUF), which is a physical structure typically within an integrated circuit that provides a number of specific outputs or responses in response to specific inputs or challenges to the PUF. Each PUF provides a discrete and unique set of responses to specific challenges, which makes PUFs suitable for use in hiding keying material in semiconductor devices for encrypting confidential information for such devices. A PUF is typically memory based and may comprise, for example, an SRAM power-up based PUF or a DRAM retention based PUF. However, as technology matures in a given node, the memory cells become more stable, which reduces the margins for implementing a PUF.